Skillshots and Hotkeys

First off, let's compare something like Ezreal's Mystic Shot to Urgot's Acid Hunter (without NCC). Both do the same thing, they fire a projectile in a straight line, for a set distance, and hit the first target they encounter.
There is a key difference though: In the heat of combat, it is easier to aim with Mystic Shot because the Interface DISPLAYS the path of your projectile. With someone like Urgot, it can be very hard to aim correctly because you are not shown that path.
The trade off is that Urgot can technically fire faster since you only have to click the Hotkey, instead of clicking the Hotkey and then mouse-clicking a target. (And also that Urgot has NCC, but lets ignore that for now)

My question is simple: Why not make using Hotkeys only an OPTION in the Interface? If a player is really good and used to their character, maybe they no longer need to see the path of their ability and can estimate it accurately. But for new players, or players trying new champions, it can be hard to get used to.

Players are already technically allowed to manually target these hotkey-activated abilities (Acid Hunter from Urgot, Lay Waste from Karthus, etc), the only difference is that they can only manually target by mouse-clicking. Why not just give us an Interface option that allows us to choose how we want to play?